Circuit breaker with thermal tripping device

ABSTRACT

A circuit breaker actuated automatically electrically for interrupting current supply from a multiphase circuit to a load accomplished by a series overcurrent tripping device. An operating coil of the main circuit interruptor has one terminal connected to one phase of the power circuit and its other terminal connected to a movable control contact in a control circuit connected to the other phase of the power circuit. The overcurrent tripping device is a bimetallic device that functions as a thermal tripping device functioning to actuate the control contact to a position closing the control circuit to energize the operating coil and interrupt the main circuit supply to the load when an overload or short circuit obtains. When the overload or short circuit is removed the bimetallic device cools and the control contact, which is biased to a rest position breaking the control circuit, is restored automatically to its rest position so that the main circuit interruptor is deenergized and automatically allows closing of its main contacts that make-andbreak the supply circuit to the load.

United States Patent Rodriguez Feb. 13, 1973 [54] CIRCUIT BREAKER WITH THERMAL Primary Examiner-James D. Trammell TRIPPING DEVICE Attorney-Robert E. Burns et al.

[76] Inventor: Arturo Perez Rodriguez, 2 rue Genera! Moscardo, Madrid, Spain [57] ABSTRACT I Filed: Feb}, 1972 A circuit breaker actuated automatically electrically Appl. No.: 223,098

Foreign Application Priority Data for interrupting current supply from a multiphase circuit to a load accomplished by a series overcurrent tripping device. An operating coil of the main circuit interruptor has one terminal connected to one phase of the power circuit and its other terminal connected to a movable control contact in a control circuit connected to the other phase of the power circuit. The

overcurrent tripping device is a bimetallic device that functions as a thermal tripping device functioning to actuate the control contact to a position closing the control circuit to energize the operating coiland interrupt the main circuit supply to the load when an overload or short circuit obtains. When the overload or short circuit is removed the bimetallic device cools and the control contact, which is biased to a rest position breaking the control circuit, is restored automatically to its rest position so that the main circuit interruptor is deenergized and automatically allows closing of its main contacts that make-and-break the supply circuit to the load.

7 Claims, 2Drawing Figures CIRCUIT BREAKER WITH THERMAL TRIPPING DEVICE BACKGROUND OF THE INVENTION The present invention relates to circuit-protective apparatus and more particularly to a circuit breaker with'a thermal tripping device.

DESCRIPTION OF THE PRIOR ART Circuit-protective apparatus comprising circuit breakers for interrupting a circuit by quick-make and quick-break contacts actuated by thermal tripping devices comprising a bimetallic element are known. The breaker automatically trips when an overload or short circuit exists and is kept open until current is at the proper value. These circuit breakers have relay means or a solenoid having an operating coil and the main contact assembly for opening the supply circuit to the equipment being protected is linked mechanically to the interrupter.

The automatic tripping is usually accomplished by a series overcurrent tripping device which may be a thermal tripping device, such as a bimetallic element, or may constitute the operating coil of the solenoid which is connected in series with the circuit in which the breaker is installed. Overloads of long duration are interrupted by these breakers which have time delay elements therein before damage is done. Short circuits are interrupted by instantaneous elements so that selective tripping systems are possible which include long-time delay and short-time delay elements to trip at different times. Many of these known circuit breakers are limited in that they are manually operated.

SUMMARY OF THE INVENTION The general purpose of the invention is to provide an automatic circuit breaker energized by the power supply circuit to which a load is connected and the supply of current of which is to be interrupted by the breaker. In accordance with the circuit breaker of the invention an electromagnetic means, for example a relay or a solenoid, has main contacts biased to a closed position and connected in operation in series with the load. An operating coil of the electromagnetic device is energizable for actuating the series contacts to an open position. A control circuit connected to the power circuit controls the energizing of the operating coil. The control circuit has a quick-make and a quick-break control contact biased to a rest position, maintaining the control circuit open and the operating coil deenergized in the absence of an overload or short circuit. This control contact is operable to a second position closing the control circuit to energize the operating coil for opening the main or principal contacts. A thermal tripping device constructed as a bimetallic elements actuates the control contact to its second position from its rest position when an overload or short circuit exists.

The operating coil is connected to a phase of the supply of the power circuit and has its opposite end terminal connected to the movable control contact. The control circuit has a fixed contact at the second position of the control contact. Provision is made for maintaining the operating coil energized when the series contacts are open by maintaining the series open by use of a resistor connected to the control circuit and one phase of the power supply in parallel with a set of main contacts which are connected to this same phase in series with the load.

ln one embodiment the circuit breaker according to the invention a second resistor is connected to maintain positive closing of the principal breaker contacts and insure that the control contact restores itself to its rest position, opening the control circuit, before the breaker main contacts are closed thereby to preclude oscillations or temporary interruptions of the circuit by the principal contacts.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic of a circuit breaker according to the invention, and

FIG. 2 is a schematic of a second embodiment of a circuit breaker according to the invention. I

Other objects and advantages appear from the following description of examples of the invention and the novel features will be particularly pointed out in the appended claims.

DESCRIPTION OF THE PREFERRED EMBODIMENTS As illustrated in FIG. 1, a multiphase power supply circuit having a phase R and a phase S has a circuit breaker according to the invention connected thereto. Across the supply circuit is connected a pair of series contacts 1,2 connected to respective phases and in series with a thermal tripping device 3 constructed as a bimetallic element or device shunted by a shunt 4 and in series with a load 5. The series contacts 1,2 constitute the main contacts of electrical magnetic means, for example a relay or a solenoid, having an operating coil 6 which has one terminal connected to the phase R and its other terminal connected to a movable control contact 7 of a control circuit having a branch circuit I and a second branch circuit D.

When an overload or short circuit exists and exceeds a certain value, the bimetallic thermal tripping device 3 is deflected or snaps in a direction, toward the right in the drawing, for actuating the control contact 7 from a normal rest position, in which the control circuit is open, to a second position in which it establishes a circuit through the control branch circuit D to energize the operating coil 6. When the operating coil 6 is energized, mechanical linkage thereto, shown in broken lines, operates the two series contacts in sequence to an open position. The series contacts are biased, for example spring biased, to a closed position so that the energizing of the operating coil opens a first series main contact 1 and sequentially a second series main contact 2.

Provision is made in the breaker, according to the in-' vention, for maintaining the operating coil energized during the existence of the overload or short circuit. Thus a resistor 8 is connected to the phase S of the power circuit and to the control circuit to allow current flow to the operating coil even though the related main contact 2 is in an open condition.

When the overload or short circuit is removed and current is within the prescribed limit, the thermal tripping device 3 cools and restores itself to its rest position, illustrated in the drawing, allowing the control contact 7 to restore itself to its rest position as illustrated in the drawing. it is understood that the control contact is normally in this rest position and is biased to its rest position.

The control circuit comprises a branch circuit I having a fixed contact at the rest position of the control contact and connected intermediate the thermal tripping device and one of the main contacts 1 as illustrated in the drawing. The second branch circuit D of the control circuit has a second fixed contact connected to the phase S of the control circuit.

A modification of this basic circuit is possible and the modification is illustrated by the broken lines representing the phase S in which case the second main contacts 2 and the related maintaining resistor 8 would be eliminated. In this case the operating coil would also remain energized during the existence of an overload or short circuit.

Provision can be made in the circuit breaker according to the invention for insuring positive operation thereof and avoiding any oscillation or temporary undesired interruptions of the main supply circuit to the load by elimination of oscillations or chatter of the main interrupter contacts 1,2. Thus in FIG. 2 a circuit breaker corresponding to the arrangement shown in FIG. 1 is illustrated. The same or corresponding reference numerals are employed in the FIGS. in order to allow easy comparison of this embodiment with the first embodiment described. The elements 1-8 are connected in a circuit configuration in this embodiment as before described. However,.in this case a second resistor 9 is connected to the control circuit at a junction between the control contact 7 and the terminal of the operating coil 6 connected thereto and is connected at a junction between the thermal tripping device and a series contact 1 as illustrated. The fixed contact of the main circuit I is connected at a junction between this second resistor 9 and its junction with the supply circuit to the load.

This second resistor functions to insure that the control contact 7 is restored to its rest position prior to closing of the main series contacts 1,2 when the overcurrent has been removed. Thus this avoids oscillations or temporary interruptions of the supply circuit since oscillations of the main contacts are avoided and the breaker accordingly functions in a positive manner to make and break the circuit being interrupted thereby.

What I claim and desire to secureby letters patent is:

1. A circuit-protective apparatus connectable to a power circuit having a load connected thereto comprising, a circuit breaker having electromagnetic means having contacts biased to a closed position and connected in operation in series with said load, means for opening said series contacts when an overload or short circuit exists comprising an operating coil energizable for actuating said series contacts to an open position, a control circuit connected to said power circuit in operation for controlling energizing of said operating coil comprising a quick-make and quick-break control contact biased to a rest position maintaining the control circuit open and the operating coil deenergized in the absence of an over load or short circuit and operable to a second position closing the control circuit to energize said operating coil for opening said series contacts, a thermal tripping device in series with said load for actuating said control contact to said second position when an overload or short circuit exists, and maintaining means connected to said power circuit and said control circuit for maintaining said operating coil energized when said series contacts are open thereby maintaining said seriescontacts open.

2. A circuit-protective apparatus connectable to a power circuit according to claim 1, in which said operating coil has a terminal connected to said power circuit and another terminal connected to said control contact, means connecting the series contacts in operation in parallel with said operating coil, said control circuit including a fixed contact connected in operation to said power circuit and contacted by said control contact in said second position thereof, means connecting said first fixed contact in operation to said power circuit defining a branch of said control circuit in parallel with said load and thermal tripping device when said control contact closes said control circuit, whereby when said control contact is in said second position said branch circuit and said operating coil are in series and in parallel with said load, said thermal tripping device and said series contacts, a second fixed contact in said control circuit contacted by said control contact in its rest position thereof, means connecting said second contact intermediate said thermal tripping device and said series contacts.

3. A circuit-protective apparatus connectable to a power circuit according to claim 2, in which said thermal tripping device comprises a deflectable bimetallic element deflecting when heated in a direction for actuating said control contact to said second position, and a shunt across said bimetallic element.

4. A circuit-protective apparatus connectable to a power circuit according to claim 3, in which said series contacts comprise a pair of contacts, means connecting said load and said thermal tripping device intermediate said pair of series contacts, and a resistor in parallel with one of said pair of series contacts connected to said power circuit and said branch circuit to maintain said operating coil energized when said one of said pair of contacts is open.

5. A circuit-protective apparatus connectable to a power circuit according to claim 1, in which said thermal tripping device comprises a bimetallic element which snaps in said direction for actuating said control contact when heated to a selected temperature corresponding to a selected overload level.

6. A circuit-protective apparatus connectable to a power circuit according to claim 1, in which said electromagnetic means comprises means for opening said series contacts in sequence, said series contacts comprising a pair of contacts each connected in operation to a respective phase of said power circuit, and said maintaining means comprising a resistor connected in use to one phase of said power circuit and said control circuit across one of the series contacts to maintain said operating coil energized when said contacts are open.

7. A circuit-protective apparatus connectable to a power circuit according to claim 1, including a resistor connected to insure said control contact restores itself to said rest position prior to closing of said series contacts thereby to avoid oscillations of said series contacts. 

1. A circuit-protective apparatus connectable to a power circuit having a load connected thereto comprising, a circuit breaker having electromagnetic means having contacts biased to a closed position and connected in operation in series with said load, means for opening said series contacts when an overload or short circuit exists comprising an operating coil energizable for actuating said series contacts to an open position, a control circuit connected to said power circuit in operation for controlling energizing of said operating coil comprising a quickmake and quick-break control contact biased to a rest position maintaining the control circuit open and the operating coil deenergized in the absence of an over load or short circuit and operable to a second position closing the control circuit to energize said operating coil for opening said series contacts, a thermal tripping device in series with said load for actuating said control contact to said second position when an overload or short circuit exists, and maintaining means connected to said power circuit and said control circuit for maintaining said operating coil energized when said series contacts are open thereby maintaining said series contacts open.
 1. A circuit-protective apparatus connectable to a power circuit having a load connected thereto comprising, a circuit breaker having electromagnetic means having contacts biased to a closed position and connected in operation in series with said load, means for opening said series contacts when an overload or short circuit exists comprising an operating coil energizable for actuating said series contacts to an open position, a control circuit connected to said power circuit in operation for controlling energizing of said operating coil comprising a quick-make and quick-break control contact biased to a rest position maintaining the control circuit open and the operating coil deenergized in the absence of an over load or short circuit and operable to a second position closing the control circuit to energize said operating coil for opening said series contacts, a thermal tripping device in series with said load for actuating said control contact to said second position when an overload or short circuit exists, and maintaining means connected to said power circuit and said control circuit for maintaining said operating coil energized when said series contacts are open thereby maintaining said series contacts open.
 2. A circuit-protective apparatus connectable to a power circuit according to claim 1, in which said operating coil has a terminal connected to said power circuit and another terminal connected to said control contact, means connecting the series contacts in operation in parallel with said operating coil, said control circuit including a fixed contact connected in operation to said Power circuit and contacted by said control contact in said second position thereof, means connecting said first fixed contact in operation to said power circuit defining a branch of said control circuit in parallel with said load and thermal tripping device when said control contact closes said control circuit, whereby when said control contact is in said second position said branch circuit and said operating coil are in series and in parallel with said load, said thermal tripping device and said series contacts, a second fixed contact in said control circuit contacted by said control contact in its rest position thereof, means connecting said second contact intermediate said thermal tripping device and said series contacts.
 3. A circuit-protective apparatus connectable to a power circuit according to claim 2, in which said thermal tripping device comprises a deflectable bimetallic element deflecting when heated in a direction for actuating said control contact to said second position, and a shunt across said bimetallic element.
 4. A circuit-protective apparatus connectable to a power circuit according to claim 3, in which said series contacts comprise a pair of contacts, means connecting said load and said thermal tripping device intermediate said pair of series contacts, and a resistor in parallel with one of said pair of series contacts connected to said power circuit and said branch circuit to maintain said operating coil energized when said one of said pair of contacts is open.
 5. A circuit-protective apparatus connectable to a power circuit according to claim 1, in which said thermal tripping device comprises a bimetallic element which snaps in said direction for actuating said control contact when heated to a selected temperature corresponding to a selected overload level.
 6. A circuit-protective apparatus connectable to a power circuit according to claim 1, in which said electromagnetic means comprises means for opening said series contacts in sequence, said series contacts comprising a pair of contacts each connected in operation to a respective phase of said power circuit, and said maintaining means comprising a resistor connected in use to one phase of said power circuit and said control circuit across one of the series contacts to maintain said operating coil energized when said contacts are open. 